Downstairs neighbors complaining about toddler noise

We had new neighbors move into the apartment below ours a couple months ago. They knocked on our door within days of moving in to tell us that our 2 year old is too loud since he is constantly running, stomping, and throwing things. I was very apologetic, told them I understood their frustration, and said we’d work on it.

We bought toddler slippers. We have him play on the rugs and carpeted areas only. We made a game out of “quiet feet”. We are constantly redirecting him and telling him to stop running and jumping and dancing and throwing. Every other word out of our mouth is “no” these days.

But he is newly 2 years old and I can’t make him behave perfectly overnight. He has tantrums and doesn’t always remember quiet feet. Every time he makes a loud noise we hear the neighbors banging on their ceiling. One of them came up for a second time after toddler ran across the living room at 1pm to tell us that we need to “discipline our kid”. We pointed to all the things we’ve done to mitigate the sound but it’s still not good enough for them.

I get that it sucks to live below a toddler but we are trying. I’m pregnant and due any day now so I’m sure issue is about to get worse. I can’t stand the animosity and I hate walking on eggshells in my own home. I also hate the constant “no no no” and rushing to appease my child every time he has a tantrum.

Has anyone been in this situation? Any advice?